This invention relates to an image reading apparatus provided with an automatic document feeder for drawing out originals stacked on a sheet supply tray and feeding to an original reading station one by one, and more particularly an image reading apparatus for reading both front and back sides of an original simultaneously.
An image reading apparatus, ordinarily called a scanner, optically reads images on the original, converts the images to electronic data and transmits that data to image forming apparatus such as an external personal computer, copier or facsimile machine. Most of image forming apparatus are provided with such image reading apparatus.
The image reading apparatus is provided with a light source for irradiating light to an original that is drawn out and fed one by one from a sheet supply tray by an automatic document feeder and an image sensor that receives the light reflected from a surface of the original. There are an image reduction type image reading apparatus that uses an image sensor such as CCD and a contact image sensor type image reading apparatus in which a line-shaped light source and a line image sensor are disposed in close proximity to an original transport path traversing a width direction of the original (a main operating direction).
For either type of the image sensors, it is important for the original in the image reading apparatus to move consistently with a predetermined and constant speed, and as closely to an image reading surface of the image reading apparatus as possible to read the original as finely as possible and without jittering. Particularly, the contact image sensor type image sensors have a much shallower focus depth compared to that of the image reduction type, so it is necessary for the original to move closer to the image reading surface of the image reading apparatus. For this reason, it is preferable that the contact image sensor is disposed in a position where the original will move as linearly thereto as possible.
However, recent image reading apparatus have been designed to have two individual reading means to simultaneously read images on both front and back sides of the originals transported one at a time by an automatic document feeder with one pass thereof without such a complex transport control as switch back.
In such conventional image reading apparatus with a two-side reading function, many apparatus use the contact image sensor type sensor disposed in an automatic document feeder for reading images on at least one side of the original to allow for the automatic document feeder to be more compact.
As an example of the prior art, Japanese Patent Publication (KOKAI) No. 11-69086 disclosed an apparatus having two reading means on both sides of an original transport path. First image reading means (the image reduction type) moves below a first platen, which is for a thick original to be placed thereupon, to read the original, and also it reads one side of the original transported on a second platen situated below large rollers of an automatic document feeder in a stationary state. Second reading means (the contact image sensor type) is disposed on a parallel linear transport path established at downstream of the transport path of the second platen. The parallel linear transport path is located next to where the original is lifted from the second platen and transported upward around an outer circumference of the transport drum 11. A double-side image reading apparatus structured to simultaneously read both sides of an original using the first and second reading means is disclosed.
However, the prior art described above has the parallel linear transport path in the direction of discharging the original after transporting the original upward along the outer circumference of the large transport roller, and the second reading means disposed in that path. The original is transported therefrom toward an upward original discharge outlet, so the automatic document feeder needs to be extended not only in the direction of discharging the original, but also in the thickness direction of the apparatus. Such an original discharge path can have only the reading station of the second reading means to be planar, and linearity for the entire transport path is not obtained. The original travels in a curved state at least in a short path, so high quality image reading is not ensured.
Also in the prior art, because the contact image type second reading means incorporated into the automatic document feeder is positioned at back of the device unit, it is difficult to clean the backup guide surface facing the reading surface of the reading unit, making maintenance a problem.
Furthermore, when mounting the second reading means to the automatic document feeder, the mounting position of the reading means can be deviated due to variations in parts or assembly errors. Such deviation in mounting position causes a shift in an angle of the reading line of the reading means with respect to the original.
In other words, the actual reading line would be shifted from a proper reading line for reading the original because of the incorrect mounting of the reading means. In such a case, when an image is formed by the image forming apparatus such as a copier or printer, the formed image is distorted by the angle with regard to the image on the original.
In view of the problems of the prior art, an object of the present invention is to provide an image reading apparatus that does not cause distorted or out-focus image data read from both sides of an original. An object of the present invention is also to provide an image reading apparatus that makes cleaning of reading surfaces of the reading means and guide surfaces facing thereto easy, resulting in good workability in maintenance. Further, the image reading apparatus is capable of reading high-quality image, and mounting adjustment of the reading means becomes easy with little errors.
In order to achieve the aforementioned objects, an image reading apparatus according to the present invention is provided with: a platen for reading an original; first reading means for reading one side of the original transported over the platen; a sheet supply tray for stacking the originals; a discharge tray for storing the originals that have been read; a sheet transport path including a sheet feeding path for guiding the originals on the sheet supply tray to the platen, and an original discharge path formed in a straight line oblique to the platen surface for lifting the originals from the platen and guiding the originals to the discharge tray; and second reading means disposed in the linear original discharge path between the platen and the discharge tray for reading the other side of the original.
Further, an image reading apparatus according to the present invention is provided with: a platen for reading an original; first reading means for reading one side of the stationary original on the platen while moving as well as for reading one side of the original transported over the platen; cover means for covering at least a part of the platen; a sheet supply tray for stacking the originals; a discharge tray for storing the originals that have been read; a sheet feed path for guiding the originals on the sheet supply tray to the platen; a discharge path disposed at an upper portion of the cover means for lifting the originals from the platen and for guiding them to a discharge tray; second reading means for reading the other side of the originals disposed in the discharge path; guide means established opposite to the second reading means for guiding the originals to be read by the second reading means and forming a part of the discharge path; and fastening means for mounting the guide means to be removable from the cover means and exposing a reading surface of the second reading means.
Further, an automatic document feeder mounted on a main body of a document reading device is provided with reading means for reading images on the original, and support means for supporting the reading means to swing freely in the original transport direction in order to adjust inclination of the original transport direction of the reading means.